This invention relates to the sailboards, and more particularly to booms thereof.
It is known that the booms for sailboards are formed substantially by two curved spars which are joined to each other at their ends so as to form a substantially elliptical member, one end of the latter being secured to the mast to which the triangular sail is connected, the free corner of the sail being secured to the other end of the boom by means of a sheet.
When at sea, the navigator clings by the hands to one of the spars of the boom so as to balance the force of the wind acting on the sail.
However, this causes an elastic deformation of the boom, the extent of which increases with the force of the wind, whereby the transverse axis of the boom tends to lengthen and, therefore, the longitudinal axis to shorten.
Since the sail is secured in a stretched condition to the boom along the longitudinal axis thereof, said shortening of the longitudinal axis causes the sail to lose its stretched condition and to become loose just when its taut or stretched condition should be more necessary.
It is the main object of this invention, to overcome the drawbacks of the conventional booms for sailboards, by providing a boom which includes means for keeping a sail automatically and constantly in a stretched condition, regardless of the extent of deformation of the boom due to stresses thereon.
According to the general aspect of the invention, the free corner of the sail is secured to the aft end of the boom with the interposition of means which transform the lateral forces acting on the boom into axial pulling forces on the sail.
According to one embodiment of the invention, the two spars of the boom are connected together at the aft end of the boom by means of a short connecting rod, provided with two converging slots each into sliding engagement with two pins secured to the free ends of the corresponding spars, the free end of the sail being connected to the said connecting rod.
By virtue of the above arrangements, the sail is kept in the stretched condition constantly, regardless of the extent of deflection of the boom spars.